This type of mounting is known, e.g., from European Patent Publication No. 0,081,085, which concerns suppressing the transfer of the operating actions of an engine to the chassis, if possible. It is also, in particular, known from this publication that the vibrations of the engine with respect to the body can be sensed by a special sensor which detects the displacement of the rubber metal mount. Special reference in this connection may be made to the description relating to FIG. 5 in the publication cited. According to this, the signal provided by the sensor is then converted by a control means with an electromechanical-hydraulic converter into a hydraulic action upon the rubber metal mount.
The present invention deals with the problem of restricting the displacement vibrations of certain engine in a motor vehicle, which especially occur in the frequency range between 8 and 10 Hz. As these vibrations can constitute a significant deterioration is so-called vibration comfort, i.e., the ride sensation that is based on the absence of vehicle vibration in the above-mentioned frequency range. It must be remembered in this context that these engine-displacement vibrations are produced by road irregularities, since the latter initially impinge upon the wheels which are suspended in a sprung fashion from the body, which in turn then transfers the impact to the engine. These wheel displacement vibrations, however, lie in a frequency range between about 2 and 3 Hz, which is usually not perceived as detrimental to vibration comfort; rather this low-frequency range at about 2-3 Hz is usually interpreted by people as simply the inevitable consequence of road irregularities.
The concern, therefore, is to prevent engine displacement vibrations, particularly those from 8-10 Hz, from penetrating into the rest of the body, from which they can then have a negative effect on vibration comfort. With the above-mentioned state of the art, it is indeed possible to restrict engine-displacement vibrations, but only incompletely, since the sensor monitoring the displacement of the rubber-metal mount in fact requires that the latter be displaced, which simply means that the rubber metal mount nonetheless still permits engine-displacement vibrations. If on the other hand, the control means were so stiff that even the slightest displacements of the rubber-metal mount were prevented by countervailing hydraulic action on the rubber metal mount, the result would simply be a so-called hard engine mounting, which in turn worsens noise comfort.